The present invention relates to the art of punching openings in a workpiece and particularly to press devices for punching elongated, hollow profiled bars, mostly aluminum extruded bars, as used in the building industry for the construction of door and window frames.
In order to better evaluate the contribution to the art of the present invention reference shall be made to FIGS. 1a-1d, schematically illustrating the traditional, state of the art technique of punching extruded bars. Hence, in FIG. 1a there is shown a punching press device generally denoted 10 of any known construction, namely usually provided with a pneumatic cylinder and piston unit 12, and male punch 14.
To base plate 16 of the device 10 there is connected a generally L-shaped extension bar 18 to which a mandrel rod 20 is fixedly connected (by bolts 22). The mandrel rod carries at its free end female punch die (xe2x80x9cmatrixxe2x80x9d) 24 with counter-opening 25 configured to back-up extruded profile 26 during the punching operation.
The mandrel rod 20 is provided with a fixable stop bracket 28 for setting the distance of the punched opening from the end of processed profiled bar 26.
It will be noted that the mandrel rod 20 is somewhat flexible and normally, when not in operation, it extends at a certain angle relative to the horizontal slanting in the direction of the punching press 10. However, when the extruded profiled bar 26 is dressed over the matrix 24 (FIG. 1b), the rod 20 becomes precisely aligned, namely slightly raised by the lower wall width W1 of the bar 26. This will ensure that the male punch 14 and the female back-up die are in exact vertical alignment with respect to each other to ensure a clean cut of the opening.
As evident from FIG. 1c, the horizontal alignment or location of the matrix 24 is ensured by a roller or the equivalent device 30 the location thereof again takes into account the side wall width W2 of the bar 26.
Now, these principles of construction and working process are common to existing punching presses as known now for decades.
These devices, however, suffer from numerous drawbacks. First, it is generally inconvenient and time-consuming to insert the sometimes quite long profiled bars 26 into the operative position of FIG. 1b, bearing in mind that only small tolerances must be left between the inner cross-section of the bar 26 and the outer shape of the female matrix 24.
Secondly, it is inconvenient to remove the stamped wall pieces of the processed bars from the opening 25 following one or several punching cycles.
Thirdly, due to the unaligned or tilted initial position of the mandrel rod 20, when not in use, it is recommended always to keep a piece of a profiled bar 26xe2x80x2 over the matrix 24xe2x80x94see FIG. 1d. This precaution measure is taken to avoid damage to the male punch 14 and/or the matrix 24 if, unintentionally, the press 10 is operated while being in the position of FIG. 1a, namely when the matrix counter opening 25 is not in exact vertical register with the opening of the male punch 14.
Lastly, should the back-up opening (25) be located off-centrally (as exemplified in FIG. 1c), and it is required to have another opening be formed exactly oppositely, at the other wall of the bar (26), it is necessary to employ a separate, additional punching device (press and matrix).
A prior art device of the above mentioned kind is disclosed in Document U.S. Pat. No. 3,489,045 relating to a tube punching device for punching openings in profiled bars comprising a male punch and a female punching matrix for backing the bar during the punching operation wherein the punching matrix is attached to an elongate mandrel rod, the mounting constituted by the punching matrix and elongated mandrel rod being permanently mounted to a supporting frame and allowed only to carry out an up and down movement and a limited degree of movement from left to right. Therefore the mounting unit is not removable in operation from the supporting frame.
These and additional drawbacks of the existing punching press devices and method of operation are designed to be overcome by the contribution of the present invention.
It is thus the general object of the present invention to substitute the fixed mandrel rod and matrix structure by a portable or non-stationary mandrel bar.
It is a further object of the invention to provide punch press devices, utilizing the concept of non-stationary mandrel rod, for the application of punched openings at two or three walls of a processed extruded bar simultaneously.
Thus, there is provided according to a first aspect of the present invention a punching press device for punching openings in profiled bars comprising a male punch and a female punching matrix for backing the bar during the punching operation characterized in that the punching matrix is attached to an elongated rod removable from the punch device, means being provided for releasably placing the rod in a position suitable for punching an opening in the profiled bar by the male punch against the female punching matrix.
According to another aspect of the present invention there is provided a method of punching openings in profiled bars by punching press device comprising a male punch die and a female punching matrix, the method comprising the steps of mounting the female punching matrix to an elongated rod, inserting the matrix and a portion of the rod into the profiled bar; and placing the assembly of matrix and rod in a position suitable for punching the opening by the male punch.
The profiled bars may be hollow or non-hollow, as the case may be.